In the technical field of scroll compressors, there has been a so-called stepped wrap scroll compressor in which a step is respectively provided at an arbitrary position along a spiral direction of both of a tip surface and a bottom land of a spiral wrap of each of a fixed scroll and an orbiting scroll, and in which a wrap height of an outer circumferential side of the spiral wrap relative to the step is made higher than a wrap height of an inner circumferential side thereof relative to the step. Since the scroll compressor can three-dimensionally compress a compressible fluid in both a circumferential direction and a height direction of the spiral wrap, it is possible to increase a planned volume ratio without increasing the winding number of the spiral wrap, and thus compactness in size and improvement in performance of the scroll compressor can be achieved.
In such stepped wrap scroll compressor, in order to reduce gas leak from a tip surface of the spiral wrap, a tip seal is respectively installed on a higher tip surface and a lower tip surface of the spiral wrap. However, with regard to the tip seal provided on the lower tip surface, its outer circumferential end repeats contact and non-contact with a bottom land due to a step provided on the bottom land of a spiral wrap of the corresponding scroll. At this time, there is a possibility that the tip seal becomes in a cantilever state to be bent, thereby becomes an extracted state from a seal groove to be caught by the step, and may become broken. Therefore, the outer circumferential end of the tip seal is usually installed away from the step.
In addition, also with regard to the tip seal installed on the lower tip surface of the spiral wrap of the orbiting scroll, at an inner circumferential end, the lower tip surface of the spiral wrap of the orbiting scroll crosses a discharge port provided in a center portion of the bottom land of the fixed scroll by revolution in an orbiting manner of the orbiting scroll, and repeats opening and closing the port. At this time, there is a possibility that the tip seal becomes in a cantilever state to be bent, thereby becomes an extracted state from the seal groove to be caught by the discharge port, and that a similar problem may occur. Therefore, the inner circumferential end of the tip seal is positioned at an outer circumferential position that is aside to the outer circumferential side from the inner circumferential end of the lower tip surface of the spiral wrap by a predetermined distance.
Similarly, also with regard to the tip seal provided in the higher tip surface of the spiral wrap of the fixed scroll and/or the orbiting scroll, there is a possibility that an outer circumferential end becomes in a cantilever state to be bent, thereby becomes an extracted state from the seal groove, and is caught between the spiral wrap and an end plate, in repeating separation and contact from/with the bottom land of the corresponding scroll. Therefore, the outer circumferential end is installed at an inner circumferential position that is aside to the inner circumferential side from the outer circumferential end of the higher tip surface of the spiral wrap by a predetermined distance.
Meanwhile, in The Publication of Japanese Patent No. 3881861 and Japanese Laid-open Patent Publication No. H8-28461, there are disclosed the following types of scroll compressors: a scroll compressor in which a tip seal is provided also at an uneven portion; a scroll compressor in which the tip seal is integrated with a tip seal of a higher and/or a lower tip surface; a scroll compressor in which separation of the tip seal is prevented by fitting a convex portion provided at one end of the tip seal provided at the uneven portion to a concave portion; a scroll compressor in which separation of the seal is prevented by fitting the tip seal provided at the uneven portion to a groove with a narrow opening and a wider inner side; a scroll compressor in which prevented are separation of the tip seal of the uneven portion and an extracted state of the tip seal that becomes in a cantilever state by pressing a tip of the other tip seal by means of an end surface of one tip seal, or by combining in a hook shape an end of one tip seal and an end of the other tip seal; etc.
In addition, in Japanese Laid-open Patent Publication No. H6-42472, there is disclosed a scroll compressor in which one or more projecting portions with a diameter equal to a width thereof are provided on a back surface of the tip seal, the projecting portions are fitted in a concave portion provided in a bottom surface of a seal groove, and in which gas leak through the seal groove is prevented. In Japanese Laid-open Patent Publication No. H6-330872, there is disclosed a scroll compressor in which a tip seal having a projection provided on a back surface thereof is elastically deformed to be fitted in a seal groove, the projection is made to contact with pressure with a concave portion provided in a bottom surface of the seal groove by means of a resilient force of the tip seal, and in which the tip seal can be held in the groove at the time of assembly. Furthermore, in Japanese Laid-open Patent Publication No. 2005-351111, there is disclosed a scroll compressor in which a tip seal is installed extending to an inner circumferential end of a spiral wrap by providing a convex portion and a concave portion that are fitted in each other at the inner circumferential ends of the tip seal and the seal groove, in which improvement of a compression efficiency is achieved, and in which damage due to an extracted state of the tip seal is prevented.